Sustained release injectable microparticles have attracted attention due to several advantages. They have high patient compliance and convenience due to less frequent injections. Higher efficacy was generally achieved with lower dose due to the maintenance of sustained and effective concentration of the drug in the blood. If necessary, these formulations could be used to achieve higher local concentration to treat specific diseases. However, manufacturing these dosage forms is challenging since the product should be sterile. Standard sterilization methods do not work with these products or adversely affect the quality of the product. Hence the product should be manufactured under aseptic conditions. Aseptic manufacturing of a microparticulate product is challenging. It was established that microparticles could be manufactured by a continuous process as reported in several patents (U.S. Pat. Nos. 5,945,126; 6,270,802; 6,361,798; 7,300,671 and 6,939,033). When making microspheres, it is preferred to produce the particles in a continuous process, such as concentrating the particles to the desired level, removing undesired particles and also removing undesired solvents and surfactants by washing. To produce microparticles in a continuous flow process, equipment is available at various size ranges. For example, in-line dynamic mixers are available at various sizes from manufacturers such as Silverson machines and Ross mixers. Similarly, in-line static mixers are available from companies such as Ross mixers, Sulzer and Komax at various sizes. However, there are not many equipment options to process the microspheres at such a faster rate. Processing involves removing the unwanted components such as excess continuous phase that also contains solvents and non-encapsulated drugs. Equipment such as dead-end filtration (e.g., PharmSep from Swecco, Stir-Cell assembly from Millipore), continuous flow centrifuges (centrifuges from Alfa Lavel) and transmembrane filtration (e.g., hollow fiber filters from GE Healthcare, Spectrum) can process microsphere suspensions. However, dead-end filtration cannot handle large volumes, requires a huge surface area and uses cumbersome equipment with moving parts. Also, clogging of filters and sieves is a common problem during dead end filtration sacrificing the efficiency during the process. For larger scale operations it is necessary to change the clogged filter/sieve and this intervention could affect the aseptic operation. Continuous flow centrifuges may have a problem of particle packing (aggregation) and also are difficult to operate under aseptic conditions. Trans-membrane filtration has a limitation due to the huge surface area requirements and very high flow rate requirement for recirculation. Filter membrane clogging is also a problem for large scale operations. Additionally, removal of small particles from the product becomes necessary in several situations since smaller particles could cause inflammation due to macrophages. Spin filters from Sartorius and vibrating sieves from Swecco are the available options to remove small particles. However, sieve clogging is the major problem for both devices; therefore they are not widely used.